9 (derived from “proteinaceous infectious particles”), can damage nerve cells [11]. Even worse, they can convert the normal prion protein into more prions, enabling them to multiply exponentially within the body and transmit among individuals through ingestion of affected tissue or direct contact of body fluid. Some prion diseases, such as fatal familial insomnia, are heritable; mutations in PRNP gene which can induce the formation of the abnormal protein were identified in those cases [12]. Prion accumulation then destroys brain tissue, creating the sponge-like holes seen in scrapie, kuru, and CJD. Unlike most other pathogens, such as bacteria or viruses, prions have no DNA – so perhaps they are not “programmed” to infect the host, but rather a tragic mistake of nature, simply a mistake in the folding process. Yet, they cause incurable, fatal diseases across species. Conclusion The history of prions is a testament to the power of scientific curiosity, perseverance, and collaboration. What began as a radical and controversial idea challenged a fundamental biological dogma and ultimately reshaped the understanding of multiple fields. As scientists continue to confront new mysteries in biology and medicine, this story serves as an inspiration: Truth is not always obvious, but with rigor, collaboration, and intellectual courage, even the most unconventional ideas can shed light on the darkest of nature’s secrets. 究竟在羊類發現的「羊搔癢症」、與食人習俗有關的 「庫魯病」，以及一種叫「克雅二氏症」的神經退化疾病 之間有甚麼關係？雖然這些致命疾病出現在不同物種中， 但它們卻有可怕的共通之處。更神秘的是，科學家無法確 定病原體，致病元兇既不是病毒，也不是細菌。當時人類 的認知無法破解這個神秘詛咒。讓我們探討這個謎團，了 解如何找出這個難以捉摸的致命元兇。 羊搔癢症：受感染的羊不受控制地抓撓背部 故事開始於18世紀的英國，那時牧羊業是經濟的基 礎。然而農民不久就面臨一個令人憂慮的問題：一些羊開 始不受控制地借柱子抓撓背部，隨後停止進食，變得一瘸 一拐，最終消瘦不堪並死亡 [1]。避免疾病傳播的唯一方 法是將病羊隔離。由於缺乏進一步調查的能力，這種怪 異的疾病很快已被遺忘 [1]。 到了20世紀中葉，科學家進行更深入的研究，嘗試 找出病原體 [1]。首先，他們成功透過將病羊的腦或脊髓 組織接種到健康羊隻身上，從而人工傳播疾病。由於潛伏 期可以長達一至兩年，這一點曾讓科學家對實驗是否成 功感到困惑。隨後，科學家嘗試透過使用當時多種能使病 原體失去活性的標準方法處理樣本組織，例如使用除菌 濾膜去除可能存在的細菌等，試圖識別病原體。在另外的 實驗中，他們還以能破壞核酸（包括 DNA 和 RNA）的電 離輻射劑量處理樣本組織，嘗試破壞當中可能含有的核 酸。可是組織依然具傳染性，使他們意識到這次的病原體 可能前所未見。腦部解剖獲得的唯一線索是神經元細胞 質出現被形容為「肥皂泡」的空泡，以及大腦中的奇怪空 洞，使大腦看起來呈海綿狀。
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